Two outbreaks of neuropathogenic equine herpesvirus type 1 with breed-dependent clinical signs.
Authors: Barbić L, Lojkić I, Stevanović V, Bedeković T, Starešina V, Lemo N, Lojkić M, Madić J
Journal: The Veterinary record
Summary
# Editorial Summary: Breed-dependent clinical manifestations of neuropathogenic EHV-1 During 2009, two consecutive outbreaks of equine herpesvirus type 1 (EHV-1) in Eastern Croatian stud farms provided a compelling case study in viral epidemiology and breed-specific disease expression. Following importation of seronegative horses from the USA, the first outbreak produced four late-stage abortions and six cases of myeloencephalopathy with high mortality (four deaths), whilst a second outbreak 100 km away—triggered by movement of a clinically healthy stallion from the first farm—resulted in 17 abortions, three perinatal deaths, and only one mild neurological case. Molecular characterisation and phylogenetic analysis confirmed identical viral genomes in both outbreaks despite their starkly different clinical presentations, ruling out strain variation as the explanatory factor. The researchers attributed this divergence to breed-dependent risk factors influencing disease manifestation, though specific genetic or physiological characteristics were not detailed. For practitioners, this outbreak highlights both the substantial risk posed by international horse movements and the importance of serological screening in imported stock; it also suggests that breed-specific susceptibility to particular EHV-1 manifestations warrants further investigation to refine risk assessment and management protocols in breeding operations.
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Practical Takeaways
- •Identical EHV-1 strains can present very different clinical pictures between herds; breed composition should be considered when assessing outbreak severity and likely outcomes
- •Serologically negative imported horses can still be EHV-1 carriers and vectors; quarantine and pre-import testing protocols must be enforced regardless of health certificates
- •Clinically healthy stallions can transmit EHV-1 between farms; use extreme caution with breeding stock movements and consider epidemiological history of source herds during breeding season outbreaks
Key Findings
- •Two geographically separate EHV-1 outbreaks in Croatia were caused by identical virus despite markedly different clinical presentations
- •First outbreak resulted in 4 abortions and 4 fatal neurological cases; second outbreak had 17 abortions with minimal neurological involvement
- •Breed-dependent risk factors significantly influenced clinical manifestations of the same EHV-1 strain between the two horse populations
- •The virus was introduced via imported USA horses and subsequently spread through inter-farm movement of a clinically healthy stallion